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Instrumental Changes

The telescope has pro gressed from a simple lead tube with two lenses used by Galileo to the incredibly complex, $1.5 billion Hubble Space Telescope orbiting 380 miles above the Earth.

PHOTO (BLACK & WHITE): The Galilean or refracting telescope produces an enlarged image with the aid of concave and convex lenses which bend light. In 1609, after fiddling with a telescope designed by an obscure Dutch lens maker, Galileo aimed his creation toward the heavens. By 1610, he had found four moons revolving around Jupiter.

DIAGRAM: The Newtonian or reflecting telescope, first made in 1671, uses mirrors and lenses to bounce light and form images. Scottish mathematician James Gregory proposed the idea in 1663, but he didn't know how to grind and polish mirrors to the desired specifications. Sir Isaac Newton did--so he gets the credit.